1. Field of the Invention
The present invention relates to a method of insert molding and more particularly to a method of molding an insert or inserts in position during the molding process.
2. Description of the Related Art
Insert injection molding is a manufacturing process that is used in a variety of different industries and products. The definition of insert molding is commonly understood to be placing an object in an injection molding tool with plastic material being injected around the inserted component to either partially or totally encapsulate the inserted component.
Injection molding is used for a variety of reasons. It may be used to reduce the number of parts in the assembly by using the injected molded plastic to mechanically hold the assembly together. It may also be used to reduce wall thickness in some applications by eliminating the need for additional walls of metal or plastic for structural strength. Injection molding may simply be used to create a stronger, more robust assembly by joining the assembly together without the use of adhesive or other less reliable fastening techniques.
However, there are several limitations to conventional insert molding. The object that is to be insert molded must be held in place in the injection molding tooling during the extreme heat and pressure of the injection molding cycle. This sometimes is difficult unless the part is shaped a certain way with special features to hold and position it correctly. Using conventional methods, this is accomplished by the use of an insert holding device, sometimes referred to as a mandrel. Using conventional methods, the object to be encapsulated is attached to the mandrel and then both objects are placed into the injection molding tool during the injection molding cycle. When the cycle is complete and the plastic has had time to solidify, the mandrel is removed from the molded assembly. This procedure is cumbersome and timeconsuming. Also, after the mandrel has been removed, the hole which was occupied by the mandrel must be filled. This hole must be filled for mechanical, aesthetic, electrical or environmental reasons.
Another limitation of conventional insert molding techniques is the difficulty of protecting the inserted part from damage or deformation during the extreme temperature and pressure of injection molding inasmuch as internal cavity pressures sometimes exceed 10,000 psi and temperatures in excess of 600.degree. F.